GHSA-27RJ-CHMQ-RH6R
Vulnerability from github – Published: 2026-03-25 12:30 – Updated: 2026-10-15 03:35In the Linux kernel, the following vulnerability has been resolved:
net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs
When shrinking the number of real tx queues, netif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush qdiscs for queues which will no longer be used.
qdisc_reset_all_tx_gt() currently serializes qdisc_reset() with qdisc_lock(). However, for lockless qdiscs, the dequeue path is serialized by qdisc_run_begin/end() using qdisc->seqlock instead, so qdisc_reset() can run concurrently with __qdisc_run() and free skbs while they are still being dequeued, leading to UAF.
This can easily be reproduced on e.g. virtio-net by imposing heavy traffic while frequently changing the number of queue pairs:
iperf3 -ub0 -c $peer -t 0 & while :; do ethtool -L eth0 combined 1 ethtool -L eth0 combined 2 done
With KASAN enabled, this leads to reports like:
BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760 ... Call Trace: ... __qdisc_run+0x133f/0x1760 __dev_queue_xmit+0x248f/0x3550 ip_finish_output2+0xa42/0x2110 ip_output+0x1a7/0x410 ip_send_skb+0x2e6/0x480 udp_send_skb+0xb0a/0x1590 udp_sendmsg+0x13c9/0x1fc0 ...
Allocated by task 1270 on cpu 5 at 44.558414s: ... alloc_skb_with_frags+0x84/0x7c0 sock_alloc_send_pskb+0x69a/0x830 __ip_append_data+0x1b86/0x48c0 ip_make_skb+0x1e8/0x2b0 udp_sendmsg+0x13a6/0x1fc0 ...
Freed by task 1306 on cpu 3 at 44.558445s: ... kmem_cache_free+0x117/0x5e0 pfifo_fast_reset+0x14d/0x580 qdisc_reset+0x9e/0x5f0 netif_set_real_num_tx_queues+0x303/0x840 virtnet_set_channels+0x1bf/0x260 [virtio_net] ethnl_set_channels+0x684/0xae0 ethnl_default_set_doit+0x31a/0x890 ...
Serialize qdisc_reset_all_tx_gt() against the lockless dequeue path by taking qdisc->seqlock for TCQ_F_NOLOCK qdiscs, matching the serialization model already used by dev_reset_queue().
Additionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state reflects an empty queue, avoiding needless re-scheduling.
{
"affected": [],
"aliases": [
"CVE-2026-23340"
],
"database_specific": {
"cwe_ids": [
"CWE-362",
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-25T11:16:31Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs\n\nWhen shrinking the number of real tx queues,\nnetif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush\nqdiscs for queues which will no longer be used.\n\nqdisc_reset_all_tx_gt() currently serializes qdisc_reset() with\nqdisc_lock(). However, for lockless qdiscs, the dequeue path is\nserialized by qdisc_run_begin/end() using qdisc-\u003eseqlock instead, so\nqdisc_reset() can run concurrently with __qdisc_run() and free skbs\nwhile they are still being dequeued, leading to UAF.\n\nThis can easily be reproduced on e.g. virtio-net by imposing heavy\ntraffic while frequently changing the number of queue pairs:\n\n iperf3 -ub0 -c $peer -t 0 \u0026\n while :; do\n ethtool -L eth0 combined 1\n ethtool -L eth0 combined 2\n done\n\nWith KASAN enabled, this leads to reports like:\n\n BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760\n ...\n Call Trace:\n \u003cTASK\u003e\n ...\n __qdisc_run+0x133f/0x1760\n __dev_queue_xmit+0x248f/0x3550\n ip_finish_output2+0xa42/0x2110\n ip_output+0x1a7/0x410\n ip_send_skb+0x2e6/0x480\n udp_send_skb+0xb0a/0x1590\n udp_sendmsg+0x13c9/0x1fc0\n ...\n \u003c/TASK\u003e\n\n Allocated by task 1270 on cpu 5 at 44.558414s:\n ...\n alloc_skb_with_frags+0x84/0x7c0\n sock_alloc_send_pskb+0x69a/0x830\n __ip_append_data+0x1b86/0x48c0\n ip_make_skb+0x1e8/0x2b0\n udp_sendmsg+0x13a6/0x1fc0\n ...\n\n Freed by task 1306 on cpu 3 at 44.558445s:\n ...\n kmem_cache_free+0x117/0x5e0\n pfifo_fast_reset+0x14d/0x580\n qdisc_reset+0x9e/0x5f0\n netif_set_real_num_tx_queues+0x303/0x840\n virtnet_set_channels+0x1bf/0x260 [virtio_net]\n ethnl_set_channels+0x684/0xae0\n ethnl_default_set_doit+0x31a/0x890\n ...\n\nSerialize qdisc_reset_all_tx_gt() against the lockless dequeue path by\ntaking qdisc-\u003eseqlock for TCQ_F_NOLOCK qdiscs, matching the\nserialization model already used by dev_reset_queue().\n\nAdditionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state\nreflects an empty queue, avoiding needless re-scheduling.",
"id": "GHSA-27rj-chmq-rh6r",
"modified": "2026-10-15T03:35:24Z",
"published": "2026-03-25T12:30:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23340"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-784472.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5bb27ad54d12de67e457d7d251198e361bef835e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5bc4e69306ed7ae02232eb4c0b23ed621a26d504"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7594467c49bfc2f4644dee0415ac2290db11fa0d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7f083faf59d14c04e01ec05a7507f036c965acf8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c69df4e0524f8de8e176ba389acd83e85f5f49d0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
Loading timeline…
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.